The Fenton reaction is a reaction for generating hydroxy radicals by a reaction of divalent iron with hydrogen peroxide to provide strong oxidation effect. Based on the strong oxidation effect, the reaction is expected to be applied in various fields such as sterilization and degradation of harmful substances and persistent pollutants (for example, a technology for soil cleanup by injecting a Fenton reaction catalyst into soil polluted with harmful substances).
A technology for improving solubility of ferrous sulfate using citric acid or the like has been developed to catalyze the Fenton reaction (see Non Patent Literature 1). In addition, there has been reported a technology for sterilizing a mold based on the strong oxidation effect of the Fenton reaction (see Patent Literature 1). However, in the cases of such conventional Fenton catalysts, divalent iron used as a catalyst is very unstable and is inevitably oxidized into trivalent iron, resulting in losing the catalytic ability in a short time.
Therefore, there is a desire to the development of a stable Fenton reaction catalyst which can maintain the state of divalent iron, which is in nature unstable, for a long period of time.
Further, in the cases of conventional Fenton reaction catalysts, trivalent iron that is present in a large amount and can be inexpensively supplied cannot be used as an iron raw material.